java天数计算函数(当前月天数、某月总天数、某月剩余天数)4种方法实现

1,Java8 LocalDate

    public static int getDaysOfMonth(String dateStr) {        LocalDate date = LocalDate.parse(dateStr + "-01");        return date.lengthOfMonth();    }

2,利用日历函数

    public static int getDaysOfMonth(String dateStr) throws ParseException {        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM");        Calendar calendar = Calendar.getInstance();        calendar.setTime(sdf.parse(dateStr));        return calendar.getActualMaximum(Calendar.DAY_OF_MONTH);    }

3,也是利用日历函数，但是不需要 throws ParseException

        public static int getDaysByDate(String dateStr){        int year= Integer.parseInt(dateStr.substring(0,4));        int month=Integer.parseInt(dateStr.substring(5,7));        Calendar c = Calendar.getInstance();        c.set(year, month, 0);        return c.get(Calendar.DAY_OF_MONTH);    }

测试样例代码： 

        String dateStr = "2023-01";        int days = getDaysOfMonth(dateStr);        System.out.println(dateStr + " has " + days + " days.");

4,当月剩余天数

         public static Integer monthEndNum(String date){        SimpleDateFormat format=new SimpleDateFormat("yyyy-MM-dd");        Date dateTime = null;        try {            dateTime = format.parse(date);        } catch (ParseException e) {            e.printStackTrace();        }        Calendar c = Calendar.getInstance();        c.setTime(dateTime);        int today = c.get(Calendar.DAY_OF_MONTH);        int last = c.getActualMaximum(Calendar.DAY_OF_MONTH);        return last - today;    }   public static void main(String[] args) {        Integer days = monthEndNum("2023-01-20");        System.out.println("2023年1月剩余天数:"+days);    }

5，获取当前月天数

    //获取当前月的天数    public static int getDaysOfCurrentMonth() {        Calendar calendar = Calendar.getInstance();        return calendar.getActualMaximum(Calendar.DAY_OF_MONTH);    }

测试代码：

    public static void main(String[] args) throws ParseException {        Date currentTime = new Date();        SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");        String dateString = formatter.format(currentTime);        System.out.println(dateString);        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy年MM月dd日HH时mm分ss秒");        String dateString2 = dateFormat.format(currentTime);        System.out.println(dateString2);        Date date1 = dateFormat.parse(dateString2);        String dateString3 = formatter.format(date1);        System.out.println(dateString3);        // 将日期字符串转换为LocalDate对象        LocalDate date = LocalDate.parse("2023-04-06");        // 将LocalDate对象格式化为指定格式的字符串        DateTimeFormatter formatter1 = DateTimeFormatter.ofPattern("yyyy年M月d日");        String formattedDate = date.format(formatter1);        System.out.println(formattedDate);        // 将格式化后的字符串转换为LocalDate对象        LocalDate parsedDate = LocalDate.parse(formattedDate, formatter1);        // 将LocalDate对象转换为指定格式的字符串        String parsedDateString = parsedDate.format(DateTimeFormatter.ofPattern("yyyy-MM-dd"));        System.out.println(parsedDateString);        // 确认两个日期字符串相等        assert parsedDateString.equals("2023-04-06");        // 确认两个LocalDate对象相等        assert parsedDate.equals(date);        System.out.println("---------------------");        String sdate="2023-04-06";        String sdate2="2023年4月6日";        String sdate3="2023-04";        String sdate4="2023年4月";        System.out.println(convertDateToChs(sdate));        System.out.println(convertToChinese(sdate));        System.out.println((convertDateToEn(sdate2)));        System.out.println((convertDateToEnglish(sdate2)));        System.out.println((convertToShortChinese(sdate3)));        System.out.println((convertToShortEnglish(sdate4)));        String dateStr = "2023-02";        int days = getDaysByDate(dateStr);        System.out.println(dateStr + " has " + days + " days.");        System.out.println("今年有" +   getDaysInCurrentYear() + " days.");        System.out.println("今年已过去" +   getDaysPassedInCurrentYear() + " days.");        System.out.println("今年剩余" +   getDaysEndInCurrentYear() + " days.");    }

测试效果截图：

来源地址：https://blog.csdn.net/wh445306/article/details/130642759